1. Field of the Invention
The present invention relates to a technique for preventing adhesion of marine organisms to an inlet channel of a plant, by using electrolysis.
2. Description of the Related Art
Marine organisms, such as mussels, barnacles, hydrozoan and marine alga, adhere to water contact surfaces (inner surfaces) of an inlet channel of a power plant, which uses seawater as a cooling water. The adhering marine organisms reduce the seawater flow rate in the inlet channel, hindering the function of the inlet channel.
For the purpose of exterminating the marine organisms and preventing adhesion of the marine organisms, various measures are taken. Such measures include: pouring chlorine or a chlorine compound into environmental seawater; coating a paint containing a toxic ion generating pigment; and generating toxic ions, such as chlorine ions or copper ions, through the electrolysis of seawater.
Although these measures exercise effective antifouling functions, the management of the quantity and concentration of those chemicals is not simple when dealing with quantities of seawater and, therefore, the chemical concentration of seawater is liable to be excessively large. Consequently, it is highly possible that the chemicals cause environmental contamination. Thus, there is a trend in recent years to inhibit or control the use of the aforesaid methods.
Recently, non-pollutive and nontoxic antifouling measures have been developed. For example, antifouling silicone paints are nontoxic and do not cause environmental pollution. However, collision of shells and foreign substances with the silicone paints shortens the effective antifouling life of the silicone paints. Coating work using antifouling silicone paints requires a high cost. Antifouling silicone paints cannot be applied to structures having large surfaces and existing structures by simple, easy coating work. The antifouling effect of antifouling silicone paints is reduced in still seawater. Due to the above disadvantages, antifouling silicone paints have not been prevalently applied to practical uses.
JP11-323868A discloses a specific arrangement of electrodes for an electrochemical antifouling system. Insoluble conductive members are arranged on wall surfaces of an underwater structure, and are connected to a positive terminal of an external direct-current power source. When the insoluble conductive members are supplied with an antifouling current, they function as positive electrodes (anodes), so that chlorine and oxygen having sterilizing effect are generated at the interface between the insoluble conductive members and seawater. Thus, adhesion of marine organisms to the wall surfaces is prevented or suppressed.
JP2000-119884 (U.S. Pat. No. 6,511,586 B1) teaches that oxygen can be generated while suppressing the generation of chlorine, by using a positive electrode (anode) coated with an electric catalyst.
In the system of JP11-323868A, the negative electrodes (cathodes) are formed of metallic strips or metallic wires, and are formed in a shape resembling a lattice, a reed-screen, a net or a spiral. The negative electrodes are held in place by insulating support members, respectively, in such a manner that each of the negative electrodes is spaced apart from the corresponding positive electrode at the same distance.
However, with the arrangement of the negative electrodes of JP11-323868A, the costly, insulating support members are absolutely necessary, and considerable time and effort are necessary to install the system. Moreover, as the negative electrodes and the support members protrude into the interior of the channel, drifting articles such as garbage are likely to be caught by the negative electrodes and the support members.
JP7-300833A discloses an antifouling system provided with a negative electrode arranged on the bottom surface of the inlet channel. In this arrangement, wide anode potential distribution exists over the positive electrode, and the anode potential of a part of the positive electrode near the negative electrode exceeds the limit for oxygen generation (1.2 V S.C.E.) to reach the range for chlorine generation. Thus, this arrangement is not suitable for an antifouling method by using oxygen.
A system, which includes titanium sheets serving as anodes, and anchor bolts for fixing the titanium sheets in place and serving as cathodes, has been proposed. The anchor bolts are electrically insulated from the titanium sheet. With this arrangement, lead wires are connected to the anchor bolts, and thereafter, the titanium plate is fastened to the anchor bolts. Thus, the install work is troublesome.
Moreover, with the above arrangement, titanium plates are provided to supply anodic current to the titanium sheets. Thus, the number of the component parts is considerably large. In addition, as four anchor bolts are necessary to fix each titanium sheet, a considerably long time is required to install the system.